Plasma processes for depositing low dielectric constant films

ABSTRACT

A method and apparatus for depositing a low dielectric constant film by reaction of an organosilicon compound and an oxidizing gas comprising carbon at a constant RF power level. Dissociation of the oxidizing gas can be increased prior to mixing with the organosilicon compound, preferably within a separate microwave chamber, to assist in controlling the carbon content of the deposited film. The oxidized organosilane or organosiloxane film has good barrier properties for use as a liner or cap layer adjacent other dielectric layers. The oxidized organosilane or organosiloxane film may also be used as an etch stop and an intermetal dielectric layer for fabricating dual damascene structures. The oxidized organosilane or organosiloxane films also provide excellent adhesion between different dielectric layers.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/647,959, filed Aug. 26, 2003, now U.S. Pat. No. 6,869,896, which is acontinuation of U.S. patent application Ser. No. 10/229,992, filed onAug. 27, 2002, now U.S. Pat. No. 6,734,115, which is a continuation ofU.S. patent application Ser. No. 09/594,186, filed on Jun. 13, 2000, nowissued as U.S. Pat. No. 6,562,690, which is a continuation of U.S.patent application Ser. No. 09/185,555, filed on Nov. 4, 1998, nowissued as U.S. Pat. No. 6,303,523, which was a continuation-in-part ofU.S. patent application Ser. No. 09/021,788, filed on Feb. 11, 1998, nowissued as U.S. Pat. No. 6,054,379, a continuation-in-part of U.S. patentapplication Ser. No. 09/114,682, filed on Jul. 13, 1998, now issued asU.S. Pat. No. 6,072,227, and a continuation-in-part of U.S. patentapplication Ser. No. 09/162,915, filed on Sep. 29, 1998, now issued asU.S. Pat. No. 6,287,990.

BACKGROUND OF THE DISCLOSURE

1. Field of the Invention

The present invention relates to the fabrication of integrated circuits.More particularly, the invention relates to a process and apparatus fordepositing dielectric layers on a substrate.

2. Background of the Invention

One of the primary steps in the fabrication of modern semiconductordevices is the formation of metal and dielectric films on a substrate bychemical reaction of gases. Such deposition processes are referred to aschemical vapor deposition or CVD. Conventional thermal CVD processessupply reactive gases to the substrate surface where heat-inducedchemical reactions take place to produce a desired film. The hightemperatures at which some thermal CVD processes operate can damagedevice structures having layers previously formed on the substrate. Apreferred method of depositing metal and dielectric films at relativelylow temperatures is plasma-enhanced CVD (PECVD) techniques such asdescribed in U.S. Pat. No. 5,362,526, entitled “Plasma-Enhanced CVDProcess Using TEOS for Depositing Silicon Oxide”, which is incorporatedby reference herein. Plasma-enhanced CVD techniques promote excitationand/or disassociation of the reactant gases by the application of radiofrequency (RF) energy to a reaction zone near the substrate surface,thereby creating a plasma of highly reactive species. The highreactivity of the released species reduces the energy required for achemical reaction to take place, and thus lowers the requiredtemperature for such PECVD processes.

Semiconductor device geometries have dramatically decreased in sizesince such devices were first introduced several decades ago. Sincethen, integrated circuits have generally followed the two year/half-sizerule (often called Moore's Law), which means that the number of devicesthat will fit on a chip doubles every two years. Today's fabricationplants are routinely producing devices having 0.35 μm and even 0.18 μmfeature sizes, and tomorrow's plants soon will be producing deviceshaving even smaller geometries.

In order to further reduce the size of devices on integrated circuits,it has become necessary to use conductive materials having lowresistivity and insulators having low k (dielectric constant <4.0) toreduce the capacitive coupling between adjacent metal lines.Liner/barrier layers have been used between the conductive materials andthe insulators to prevent diffusion of byproducts such as moisture ontothe conductive material as described in International Publication NumberWO 94/01885. For example, moisture that can be generated duringformation of a low k insulator readily diffuses to the surface of theconductive metal and increases the resistivity of the conductive metalsurface. A barrier/liner layer formed from conventional silicon oxide orsilicon nitride materials can block the diffusion of the byproducts.However, the barrier/liner layers typically have dielectric constantsthat are significantly greater than 4.0, and the high dielectricconstants result in a combined insulator that does not significantlyreduce the dielectric constant.

FIG. 1A illustrates a PECVD process for depositing a barrier/liner layeras described in International Publication Number WO 94/01885. The PECVDprocess deposits a multi-component dielectric layer wherein a silicondioxide (SiO₂) liner layer 2 is first deposited on a patterned metallayer having metal lines 3 formed on a substrate 4. The liner layer 2 isdeposited by a plasma enhanced reaction of silane (SiH₄) and nitrousoxide (N₂O) at 300° C. A self-planarizing low k dielectric layer 5 isthen deposited on the liner layer 2 by reaction of a silane compound anda peroxide compound. The self-planarizing layer 5 retains moisture thatis removed by curing. The liner layer 2 is an oxidized silane film thathas effective barrier properties when deposited in a manner whichprovides a dielectric constant of at least 4.5. The dielectric constantof the oxidized silane film can be decreased to about 4.1 by alteringprocess conditions in a manner that decreases moisture barrierproperties of the film. Conventional liner layers, such as SiN, haveeven higher dielectric constants, and the combination of low kdielectric layers with high k dielectric liner layers can provide littleor no improvement in the overall stack dielectric constant andcapacitive coupling.

As shown in FIG. 1B, WO 94/01885 further describes an optional SiO₂ caplayer 6 that is deposited on the low k dielectric layer 5 by thereaction of silane and N₂O. The cap layer 6 is also an oxidized silanefilm that has good barrier properties when deposited in a manner thatprovides a dielectric constant of about 4.5. Both the liner layer 2 andthe cap layer 6 have a dielectric constant greater than 4.5 and the highdielectric constant layers substantially detract from the benefit of thelow k dielectric layer 5.

As devices get smaller, liner layers and cap layers having highdielectric constants contribute more to the overall dielectric constantof a multi-component dielectric layer. Furthermore, known low kdielectric materials generally have low oxide content which makes thematerial inadequate as an etch stop layer during etching of vias and/orinterconnects. Silicon nitride has been the etch stop material of choicefor making interconnect lines in low k dielectric materials. However,the silicon nitride has a relatively high dielectric constant(dielectric constant of about 7) compared to the surrounding low kdielectric layers. It has also been discovered that the silicon nitridemay significantly increase the capacitive coupling between interconnectlines, even when an otherwise low k dielectric material is used as theprimary insulator. This may lead to crosstalk and/orresistance-capacitance (RC) delay that degrades the overall performanceof the device. Thus, the silicon nitride etch stop layers are typicallyremoved after etching of the underlying dielectric layers.

Ideally, a low k dielectric layer having both good barrier propertiesfor use as a liner layer and sufficient oxide content for use as an etchstop could be identified and deposited in the same chambers as existinglow k dielectric materials. Such barrier layers would not increase theoverall dielectric constant of the dielectric layers, and such an etchstop layer would not have to be removed after etching the underlyinglayers.

U.S. Pat. No. 5,554,570 describes barrier layers for use with thermalCVD silicon oxides wherein an organosilane having a C—H group isoxidized instead of silane to increase the density of deposited filmsand to improve adhesion between the layers. For example, a thermal CVDlayer produced from tetraethoxysilane (TEOS) and ozone, may be depositedbetween PECVD silicon oxide films produced from an organosilicon and N₂Oor O₂.

The barrier layers described in the '570 patent are preferably densesilicon oxide layers having low carbon contents. The dense layers aredeposited using 400 W of high frequency RF power although the use of lowfrequency RF power is asserted to improve film stress. The barrierlayers are preferably produced from alkoxysilanes or chlorinatedalkylsilanes and N₂O to reduce carbon content and increase the densityof the layers.

The '570 patent does not identify process conditions for making barrierlayers having low dielectric constants or for making etch stop layershaving high oxide contents. The '570 patent also does not suggest use ofthe described layers as a barrier layer adjacent a low k dielectriclayer or as an etch stop.

There remains a need for dielectric layers having low dielectricconstants, good barrier properties, and high oxide content for use asbarrier layers or etch stop layers in sub-micron devices.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for depositing asilicon oxide layer having a low dielectric constant. The silicon oxidelayer is produced by plasma assisted chemical vapor deposition of anorganosilane, an organosiloxane, or combinations thereof, using RF ormicrowave power to generate reactive oxygen atoms. The properties of thesilicon oxide layers are readily controlled by process variations, anddifferent layers can be deposited in one deposition chamber as shown foran improved dual damascene process. In addition, the silicon oxidelayers can be used as an adhesive layer between different layers, or asan intermetal dielectric layer. A preferred silicon oxide layer isproduced by reaction of nitrous oxide, N₂O, and a silicon compoundcontaining Si—H bonds, such as methylsilane, CH₃SiH₃, or dimethylsilane,(CH₃)₂SiH₂.

The silicon oxide layers are cured at low pressure and high temperatureto stabilize properties. The silicon oxide layers are most preferablyproduced using separate applications of RF power to the depositionchamber to increase porosity of the deposited layers. The use of lowlevels of RF power is preferred at chamber pressures less than about 10Torr. Microwave power is preferably provided to oxidizing gases in adissociation chamber to control formation of reactive oxidizers withoutincreasing the power level in the deposition chamber.

In a preferred embodiment, a silicon oxide layer is deposited on apatterned metal layer by plasma assisted reaction of one or moreorganosilane and/or organosiloxane compounds that include Si—H bonds.

The silicon oxide of the present invention has further utility in anintegrated process for manufacture of reliable dual damascene structuresin one deposition chamber to reduced capacitive coupling betweeninterconnect lines. In a preferred embodiment, a low k dielectric filmhaving high carbon content, greater than about 20% by atomic weight, isdeposited as a via level dielectric layer. A low k dielectric filmhaving a low carbon content, less than about 10% by atomic weight, isthen deposited on the high carbon layer to form a trench leveldielectric layer. A dual damascene etch then forms the trenches in thetrench level dielectric layer and stops at the via level dielectriclayer. After etching the vias in the via level dielectric layer, theupper surface is then planarized to leave a planar surface on the trenchlevel dielectric layer.

The invention further provides an intermetal dielectric material (IMD)comprising the silicon oxide which is deposited on a conventional etchstop such as silicon oxide or silicon nitride. The silicon oxide canalso be deposited as a thin adhesive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobjects of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the embodiments thereofwhich are illustrated in the appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1A-1B (Prior Art) are schematic diagrams of dielectric layersdeposited on a substrate by the processes known in the art;

FIG. 2 is a cross-sectional diagram of an exemplary CVD plasma reactorconfigured for use according to the present invention;

FIG. 3 is a diagram of the system monitor of the CVD plasma reactor ofFIG. 2;

FIG. 4 is a flow chart of a process control computer program productused in conjunction with the exemplary CVD plasma reactor of FIG. 2;

FIG. 5 is a flow chart illustrating steps undertaken in depositing linerand cap layers in a gap filling process according to one embodiment ofthe present invention;

FIG. 6A-6E is a schematic diagram of the layers deposited on a substrateby the process of FIG. 5;

FIG. 7 is a cross sectional view showing a dual damascene structurecomprising the silicon oxide layers of the present invention;

FIGS. 8A-8H are cross sectional views showing one embodiment of a dualdamascene deposition sequence of the present invention;

FIG. 9 is a cross sectional view showing an adhesive layer comprisingthe silicon oxide layer of the present invention between a premetaldielectric layer and an intermetal dielectric layer;

FIGS. 10A-10H are cross sectional views showing a dual damascenedeposition sequence wherein the silicon oxide of the present inventionis used to adhere an intermetal dielectric film to a conventional etchstop; and

FIGS. 11A-11D are cross sectional views showing an integrated dualdamascene deposition sequence wherein the silicon oxide of the presentinvention is used to eliminate a conventional etch stop.

For a further understanding of the present invention, reference shouldbe made to the ensuing detailed description.

DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention provides a method and apparatus for depositing asilicon oxide layer having a low dielectric constant, a high oxidecontent, and sufficient carbon content to provide barrier properties.The silicon oxide layer comprises an oxidized organosilane ororganosiloxane and can be used as a lining layer adjacent otherdielectric materials, as an etch stop layer adjacent dielectricmaterials having lower oxide content, as an intermetal dielectric layer,and as an adhesion layer between different materials. The oxidizedorganosilane material is deposited by plasma assisted oxidation of theorganosilane or organosiloxane compounds using from about 10 W to about200 W of constant RF power, or from about 20 W to about 500 W of pulsedRF power. The silicon oxide layer can also be deposited using frequentbreaks, such as changing chambers or providing cooling time, to improveporosity. The RF power is preferably provided at a high frequency suchas between 13 MHz and 14 MHz. The RF power is preferably provided inshort duration cycles wherein the power is on at the stated levels forcycles less than about 200 Hz and the on cycles total from about 10% toabout 30% of the total duty cycle. Intermittent RF power can operate athigher peak power levels and provide the same total power input asconstant RF power at a lower power level.

Carbon which remains in the silicon oxide layer contributes to lowdielectric constants and barrier properties. The remaining carbon isbetween about 1% and about 50% by atomic weight, and preferably includessufficient C—H or C—F bonds to provide hydrophobic properties to thesilicon oxide layer resulting in significantly lower dielectricconstants and improved moisture barrier properties.

The silicon oxide layers are produced from silicon compounds thatinclude carbon in organo groups that are not readily removed byoxidation at processing conditions. Preferably the —C—H bonds areincluded such as in alkyl or aryl groups, or fluorinated carbonderivatives thereof. Suitable organo groups also can include alkenyl andcyclohexenyl groups and functional derivatives. The organo siliconcompounds include:

methylsilane, CH₃—SiH₃ dimethylsilane, (CH₃)₂—SiH₂ trimethylsilane,(CH₃)₃—SiH dimethylsilanediol, (CH₃)₂—Si—(OH)₂ ethylsilane, CH₃—CH₂—SiH₃phenylsilane, C₆H₅—SiH₃ diphenylsilane, (C₆H₅)₂—SiH₂ diphenylsilanediol,(C₆H₅)₂—Si—(OH)₃ methylphenylsilane, C₆H₅—SiH₂—CH₃ disilanomethane,SiH₃—CH₂—SiH₃ bis(methylsilano)methane, CH₃—SiH₂—CH₂—SiH₂—CH₃1,2-disilanoethane, SiH₃—CH₂—CH₂—SiH₃ 1,2-bis(methylsilano)ethane,CH₃—SiH₂—CH₂—CH₂—SiH₂—CH₃ 2,2-disilanopropane, SiH₃—C(CH₃)₂—SiH₃1,3,5-trisilano-2,4,6-trimethylene, —(—SiH₂CH₂—)₃— (cyclic)1,3-dimethyldisiloxane, CH₃—SiH₂—O—SiH₂—CH₃1,1,3,3-tetramethyldisiloxane, (CH₃)₂—SiH—O—SiH—(CH₃)₂hexamethyldisiloxane, (CH₃)₃—Si—O—Si—(CH₃)₃1,3-bis(silanomethylene)disiloxane, (SiH₃—CH₂—SiH₂—)₂—Obis(1-methyldisiloxanyl)methane, (CH₃—SiH₂—O—SiH₂—)₂—CH₂2,2-bis(1-methyldisiloxanyl)propane, (CH₃—SiH₂—O—SiH₂—)₂—C(CH₃)₂1,3,5,7-tetramethylcyclotetrasiloxane, —(—SiHCH₃—O—)₄— (cyclic)octamethylcyclotetrasiloxane, and —(—Si(CH₃)₂—O—)₄— (cyclic)1,3,5,7,9-pentamethylcyclopentasiloxane, —(—SiHCH₃—O—)₅— (cyclic)1,3,5,7-tetrasilano-2,6-dioxy-4,8-dimethylene, —(—SiH₂—CH₂—SiH₂—O—)₂—(cyclic)

The organo silicon compounds are oxidized during deposition by reactionwith oxygen (O₂) or oxygen containing compounds such as nitrous oxide(N₂O), ozone (O₃), carbon dioxide (CO₂), and water (H₂O), preferablyN₂O, such that the carbon content of the deposited film is from 1 to 50%by atomic weight, preferably about 5 to 30%. The oxidized organo siliconlayer has a dielectric constant of about 3.0 and has excellent barrierproperties. The oxidized organo silicon layers further have high oxidecontents in comparison to conventional low k dielectric layers and goodadhesion properties.

Oxygen and oxygen containing compounds are preferably dissociated toincrease reactivity when necessary to achieve a desired carbon contentin the deposited film. RF power can be coupled to the deposition chamberto increase dissociation of the oxidizing compounds. The oxidizingcompounds may also be dissociated in a microwave chamber prior toentering the deposition chamber to reduce excessive dissociation of thesilicon containing compounds. Deposition of the silicon oxide layer canbe continuous or discontinuous. Although deposition preferably occurs ina single deposition chamber, the layer can be deposited sequentially intwo or more deposition chambers. Furthermore, RF power can be cycled orpulsed to reduce heating of the substrate and promote greater porosityin the deposited film.

The organosilane and organosiloxane compounds preferably include thestructures:

wherein each Si is bonded to one or two carbon atoms, and C is includedin an organo group, preferably alkyl or alkenyl groups such as —CH₃,—CH₂—CH₃, —CH₂—, or —CH₂—CH₂—, or fluorinated carbon derivativesthereof. The carbon atoms in the fluorinated derivatives may bepartially or fully fluorinated to replace hydrogen atoms. When anorganosilane or organosiloxane compound includes two or more Si atoms,each Si is separated from another Si by O, C, or —C—C—, wherein C isincluded in an organo group, preferably alkyl or alkenyl groups such asCH₂, CH₂CH₂, CH(CH₃) or C(CH₃)₂, or fluorinated derivatives thereof. Thepreferred organosilane and organosiloxane compounds are gases or liquidsnear room temperature and can be volatilized above about 10 Torr.Preferred organosilanes and organosiloxanes include:

methylsilane, CH₃—SiH₃ dimethylsilane, (CH₃)₂—SiH₂ trimethylsilane,(CH₃)₃—SiH disilanomethane, SiH₃—CH₂—SiH₃ bis(methylsilano)methane,CH₃—SiH₂—CH₂—SiH₂—CH₃ 1,2-disilanoethane, SiH₃—CH₂—CH₂—SiH₃1,2-bis(methylsilano)ethane, CH₃—SiH₂—CH₂—CH₂—SiH₂—CH₃2,2-disilanopropane, SiH₃—C(CH₃)₂—SiH₃1,3,5-trisilano-2,4,6-trimethylene, —(—SiH₂CH₂—)₃— (cyclic)1,3-dimethyldisiloxane, CH₃—SiH₂—O—SiH₂—CH₃1,3-bis(silanomethylene)disiloxane, (SiH₃—CH₂—SiH₂—)₂—Obis(1-methyldisiloxanyl)methane, (CH₃—SiH₂—O—SiH₂—)₂—CH₂2,2-bis(1-methyldisiloxanyl)propane, (CH₃—SiH₂—O—SiH₂—)₂—C(CH₃)₂1,3,5,7-tetramethylcyclotetrasiloxane, —(—SiHCH₃—O—)₄— (cyclic)1,3,5,7,9-pentamethylcyclopentasiloxane, and —(—SiHCH₃—O—)₅— (cyclic)1,3,5,7-tetrasilano-2,6-dioxy-4,8-dimethylene, —(—SiH₂—CH₂—SiH₂—O—)₂—(cyclic) and fluorinated carbon derivatives thereof, such as:1,2-disilanotetrafluoroethane. SiH₃—CF₂—CF₂—SiH₃

The hydrocarbon groups in the organosilanes and organosiloxane may bepartially or fully fluorinated to convert C—H bonds to C—F bonds. Manyof the preferred organosilane and organosiloxane compounds arecommercially available. A combination of two or more of theorganosilanes or organosiloxanes can be employed to provide a blend ofdesired properties such as dielectric constant, oxide content,hydrophobicity, film stress, and plasma etching characteristics.

The organosilane and organosiloxane compounds are preferably oxidizedduring deposition by plasma assisted reaction with oxygen which isformed during the deposition process by decomposition of nitrous oxide(N₂O). Nitrous oxide does not react with the organosilanes ororganosiloxanes without plasma assistance, and the oxygen-nitrogen bondsare readily broken at lower energies than the bonds in the organosilanesand organosiloxanes. The oxidized compounds adhere to contacted surfacessuch as a patterned layer of a semiconductor substrate to form adeposited film. The deposited films are cured at low pressure and attemperatures from about 100 to about 450° C., preferably above about400° C. to stabilize the barrier properties of the films. The depositedfilm has sufficient carbon content to provide barrier properties. Thecarbon content preferably includes C—H or C—F bonds to provide ahydrophobic film that is an excellent moisture barrier.

The present invention further provides a substrate processing systemhaving a vessel including a reaction zone, a substrate holder forpositioning a substrate in the reaction zone, and a vacuum system. Theprocessing system further comprises a gas/liquid distribution systemconnecting the reaction zone of the vessel to supplies of anorganosilane or organosiloxane compound, an oxidizing gas, and an inertgas, and an RF generator coupled to the gas distribution system forgenerating a plasma in the reaction zone. The processing system furthercomprises a controller comprising a computer for controlling the vessel,the gas distribution system, and the RF generator, and a memory coupledto the controller, the memory comprising a computer usable mediumcomprising a computer readable program code for selecting the processsteps of depositing a low dielectric constant film with a plasma of anorganosilane or organosiloxane compound and an oxidizing gas.

The processing system may further comprise in one embodiment computerreadable program code for selecting the process steps of depositing aliner of the oxidized organo silicon compound, depositing a differentdielectric layer, and optionally depositing a capping layer of theoxidized organo silicon compound.

Further description of the invention relates to a specific apparatus fordepositing silicon oxide layers of the present invention and topreferred silicon oxide films.

Exemplary CVD Plasma Reactor

One suitable CVD plasma reactor in which a method of the presentinvention can be carried out is shown in FIG. 2, which is a vertical,cross-section view of a parallel plate chemical vapor deposition reactor10 having a high vacuum region 15. Reactor 10 contains a gasdistribution manifold 11 for dispersing process gases through perforatedholes in the manifold to a substrate or wafer (not shown) that rests ona substrate support plate or susceptor 12 which is raised or lowered bya lift motor 14. A liquid injection system (not shown), such astypically used for liquid injection of TEOS, may also be provided forinjecting a liquid organosilane and/or organosiloxane compound. Thepreferred methylsilanes are gases.

The reactor 10 includes heating of the process gases and substrate, suchas by resistive heating coils (not shown) or external lamps (not shown).Referring to FIG. 2, susceptor 12 is mounted on a support stem 13 sothat susceptor 12 (and the wafer supported on the upper surface ofsusceptor 12) can be controllably moved between a lowerloading/off-loading position and an upper processing position which isclosely adjacent to manifold 11.

When susceptor 12 and the wafer are in processing position 14, they aresurrounded by a an insulator 17 and process gases exhaust into amanifold 24. During processing, gases inlet to manifold 11 are uniformlydistributed radially across the surface of the wafer. A vacuum pump 32having a throttle valve controls the exhaust rate of gases from thechamber.

Before reaching manifold 11, deposition and carrier gases are inputthrough gas lines 18 into a mixing system 19 where they are combined andthen sent to manifold 11. An optional microwave applicator 28 can belocated on the input gas line for the oxidizing gas to provideadditional energy that dissociates only the oxidizing gas. The microwaveapplicator provides from 0 to 6000 W. Generally, the process gasessupply line 18 for each of the process gases also includes (i) safetyshut-off valves (not shown) that can be used to automatically ormanually shut off the flow of process gas into the chamber, and (ii)mass flow controllers (also not shown) that measure the flow of gasthrough the gas supply lines. When toxic gases are used in the process,several safety shut-off valves are positioned on each gas supply line inconventional configurations.

The deposition process performed in reactor 10 can be either a thermalprocess or a plasma enhanced process. In a plasma process, a controlledplasma is typically formed adjacent to the wafer by RF energy applied todistribution manifold 11 from RF power supply 25 (with susceptor 12grounded). Alternatively, RF power can be provided to the susceptor 12or RF power can be provided to different components at differentfrequencies. RF power supply 25 can supply either single or mixedfrequency RF power to enhance the decomposition of reactive speciesintroduced into the high vacuum region 15. A mixed frequency RF powersupply typically supplies power at a high RF frequency (RF1) of 13.56MHz to the distribution manifold 11 and at a low RF frequency (RF2) of360 KHz to the susceptor 12. The silicon oxide layers of the presentinvention are most preferably produced using low levels of constant highfrequency RF power or pulsed levels of high frequency RF power. PulsedRF power preferably provides 13.56 MHz RF power at about 20 W to about500 W, most preferably from 20 W to about 250 W, during about 10% toabout 30% of the duty cycle. Constant RF power preferably provides 13.56MHz RF power at about 10 W to about 200 W, preferably from about 20 W toabout 100 W. Low power deposition preferably occurs at a temperaturerange from about −20° C. to about 40° C. At the preferred temperaturerange, the deposited film is partially polymerized during deposition andpolymerization is completed during subsequent curing of the film.

When additional dissociation of the oxidizing gas is desired, anoptional microwave chamber can be used to input from 0 to 3000 W ofmicrowave power to the oxidizing gas prior to entering the depositionchamber. Separate addition of microwave power would avoid excessivedissociation of the silicon compounds prior to reaction with theoxidizing gas. A gas distribution plate having separate passages for thesilicon compound and the oxidizing gas is preferred when microwave poweris added to the oxidizing gas.

Typically, any or all of the chamber lining, distribution manifold 11,susceptor 12, and various other reactor hardware is made out of materialsuch as aluminum or anodized aluminum. An example of such a CVD reactoris described in U.S. Pat. No. 5,000,113, entitled A Thermal CVD/PECVDReactor and Use for Thermal Chemical Vapor Deposition of Silicon Dioxideand In-situ Multi-step Planarized Process, issued to Wang et al. andassigned to Applied Materials, Inc., the assignee of the presentinvention.

The lift motor 14 raises and lowers susceptor 12 between a processingposition and a lower, wafer-loading position. The motor, the gas mixingsystem 19, and the RF power supply 25 are controlled by a systemcontroller 34 over control lines 36. The reactor includes analogassemblies, such as mass flow controllers (MFCs) and standard or pulsedRF generators, that are controlled by the system controller 34 whichexecutes system control software stored in a memory 38, which in thepreferred embodiment is a hard disk drive. Motors and optical sensorsare used to move and determine the position of movable mechanicalassemblies such as the throttle valve of the vacuum pump 32 and motorfor positioning the susceptor 12.

The system controller 34 controls all of the activities of the CVDreactor and a preferred embodiment of the controller 34 includes a harddisk drive, a floppy disk drive, and a card rack. The card rack containsa single board computer (SBC), analog and digital input/output boards,interface boards and stepper motor controller boards. The systemcontroller conforms to the Versa Modular Europeans (VME) standard whichdefines board, card cage, and connector dimensions and types. The VMEstandard also defines the bus structure having a 16-bit data but and24-bit address bus.

The system controller 34 operates under the control of a computerprogram stored on the hard disk drive 38. The computer program dictatesthe timing, mixture of gases, RF power levels, susceptor position, andother parameters of a particular process. The interface between a userand the system controller is via a CRT monitor 40 and light pen 44 whichare depicted in FIG. 3. In the preferred embodiment a second monitor 42is used, the first monitor 40 being mounted in the clean room wall forthe operators and the other monitor 42 behind the wall for the servicetechnicians. Both monitors 40, 42 simultaneously display the sameinformation but only one light pen 44 is enabled. The light pen 44detects light emitted by CRT display with a light sensor in the tip ofthe pen. To select a particular screen or function, the operator touchesa designated area of the display screen and pushes the button on the pen44. The touched area changes its highlighted color, or a new menu orscreen is displayed, confirming communication between the light pen andthe display screen.

Referring to FIG. 4, the process can be implemented using a computerprogram product 410 that runs on, for example, the system controller 34.The computer program code can be written in any conventional computerreadable programming language such as for example 68000 assemblylanguage, C, C++, or Pascal. Suitable program code is entered into asingle file, or multiple files, using a conventional text editor, andstored or embodied in a computer usable medium, such as a memory systemof the computer. If the entered code text is in a high level language,the code is compiled, and the resultant compiler code is then linkedwith an object code of precompiled windows library routines. To executethe linked compiled object code, the system user invokes the objectcode, causing the computer system to load the code in memory, from whichthe CPU reads and executes the code to perform the tasks identified inthe program.

FIG. 4 shows an illustrative block diagram of the hierarchical controlstructure of the computer program 410. A user enters a process setnumber and process chamber number into a process selector subroutine 420in response to menus or screens displayed on the CRT monitor 40 by usingthe light pen 44 interface. The process sets are predetermined sets ofprocess parameters necessary to carry out specified processes, and areidentified by predefined set numbers. The process selector subroutine420 the (i) selects a desired process chamber on a cluster tool such asan Centura® platform (available from Applied Materials, Inc.), and (ii)selects a desired set of process parameters needed to operate theprocess chamber for performing the desired process. The processparameters for performing a specific process relate to processconditions such as, for example, process gas composition and flow rates,temperature, pressure, plasma conditions such as RF bias power levelsand magnetic field power levels, cooling gas pressure, and chamber walltemperature and are provided to the user in the form of a recipe. Theparameters specified by the recipe are entered utilizing the lightpen/CRT monitor interface.

The signals for monitoring the process are provided by the analog inputand digital input boards of system controller and the signals forcontrolling the process are output on the analog output and digitaloutput boards of the system controller 34.

A process sequencer subroutine 430 comprises program code for acceptingthe identified process chamber and set of process parameters from theprocess selector subroutine 420, and for controlling operation of thevarious process chambers. Multiple users can enter process set numbersand process chamber numbers, or a user can enter multiple processchamber numbers, so the sequencer subroutine 430 operates to schedulethe selected processes in the desired sequence. Preferably the sequencersubroutine 430 includes computer readable program code to perform thesteps of (i) monitoring the operation of the process chambers todetermine if the chambers are being used, (ii) determining whatprocesses are being carried out in the chambers being used, and (iii)executing the desired process based on availability of a process chamberand type of process to be carried out. Conventional methods ofmonitoring the process chambers can be used, such as polling. Whenscheduling which process is to be executed, the sequencer subroutine 430can be designed to take into consideration the present condition of theprocess chamber being used in comparison with the desired processconditions for a selected process, or the “age” of each particular userentered request, or any other relevant factor a system programmerdesires to include for determining the scheduling priorities.

Once the sequencer subroutine 430 determines which process chamber andprocess set combination is going to be executed next, the sequencersubroutine 430 causes execution of the process set by passing theparticular process set parameters to a chamber manager subroutine 440which controls multiple processing tasks in a process chamber 10according to the process set determined by the sequencer subroutine 430.For example, the chamber manager subroutine 440 comprises program codefor controlling CVD process operations in the process chamber 10. Thechamber manager subroutine 440 also controls execution of variouschamber component subroutines which control operation of the chambercomponent necessary to carry out the selected process set. Examples ofchamber component subroutines are susceptor control subroutine 450,process gas control subroutine 460, pressure control subroutine 470,heater control subroutine 480, and plasma control subroutine 490. Thosehaving ordinary skill in the art would readily recognize that otherchamber control subroutines can be included depending on what processesare desired to be performed in the reactor 10.

In operation, the chamber manager subroutine 440 selectively schedulesor calls the process component subroutines in accordance with theparticular process set being executed. The chamber manager subroutine440 schedules the process component subroutines similarly to how thesequencer subroutine 430 schedules which process chamber 10 and processset is to be executed next. Typically, the chamber manager subroutine440 includes steps of monitoring the various chamber components,determining which components needs to be operated based on the processparameters for the process set to be executed, and causing execution ofa chamber component subroutine responsive to the monitoring anddetermining steps.

Operation of particular chamber component subroutines will now bedescribed with reference to FIG. 4. The susceptor control positioningsubroutine 450 comprises program code for controlling chamber componentsthat are used to load the substrate onto the susceptor 12, andoptionally to lift the substrate to a desired height in the reactor 10to control the spacing between the substrate and the gas distributionmanifold 11. When a substrate is loaded into the reactor 10, thesusceptor 12 is lowered to receive the substrate, and thereafter, thesusceptor 12 is raised to the desired height in the chamber, to maintainthe substrate at a first distance or spacing from the gas distributionmanifold 11 during the CVD process. In operation, the susceptor controlsubroutine 450 controls movement of the susceptor 12 in response toprocess set parameters that are transferred from the chamber managersubroutine 440.

The process gas control subroutine 460 has program code for controllingprocess gas composition and flow rates. The process gas controlsubroutine 460 controls the open/close position of the safety shut-offvalves, and also ramps up/down the mass flow controllers to obtain thedesired gas flow rate. The process gas control subroutine 460 is invokedby the chamber manager subroutine 440, as are all chamber componentssubroutines, and receives from the chamber manager subroutine processparameters related to the desired gas flow rates. Typically, the processgas control subroutine 460 operates by opening the gas supply lines, andrepeatedly (i) reading the necessary mass flow controllers, (ii)comparing the readings to the desired flow rates received from thechamber manager subroutine 440, and (iii) adjusting the flow rates ofthe gas supply lines as necessary. Furthermore, the process gas controlsubroutine 460 includes steps for monitoring the gas flow rates forunsafe rates, and activating the safety shut-off valves when an unsafecondition is detected.

In some processes, an inert gas such as helium or argon is flowed intothe reactor 10 to stabilize the pressure in the chamber before reactiveprocess gases are introduced into the chamber. For these processes, theprocess gas control subroutine 460 is programmed to include steps forflowing the inert gas into the chamber 10 for an amount of timenecessary to stabilize the pressure in the chamber, and then the stepsdescribed above would be carried out. Additionally, when a process gasis to be vaporized from a liquid precursor, for example1,3,5-trisilano-2,4,6-trimethylene (1,3,5-trisilanacyclo-hexane), theprocess gas control subroutine 460 would be written to include steps forbubbling a delivery gas such as helium through the liquid precursor in abubbler assembly. For this type of process, the process gas controlsubroutine 460 regulates the flow of the delivery gas, the pressure inthe bubbler, and the bubbler temperature in order to obtain the desiredprocess gas flow rates. As discussed above, the desired process gas flowrates are transferred to the process gas control subroutine 460 asprocess parameters. Furthermore, the process gas control subroutine 460includes steps for obtaining the necessary delivery gas flow rate,bubbler pressure, and bubbler temperature for the desired process gasflow rate by accessing a stored table containing the necessary valuesfor a given process gas flow rate. Once the necessary values areobtained, the delivery gas flow rate, bubbler pressure and bubblertemperature are monitored, compared to the necessary values and adjustedaccordingly.

The pressure control subroutine 470 comprises program code forcontrolling the pressure in the reactor 10 by regulating the size of theopening of the throttle valve in the exhaust pump 32. The size of theopening of the throttle valve is set to control the chamber pressure tothe desired level in relation to the total process gas flow, size of theprocess chamber, and pumping set point pressure for the exhaust pump 32.When the pressure control subroutine 470 is invoked, the desired, ortarget pressure level is received as a parameter from the chambermanager subroutine 440. The pressure control subroutine 470 operates tomeasure the pressure in the reactor 10 by reading one or moreconventional pressure manometers connected to the chamber, compare themeasure value(s) to the target pressure, obtain PID (proportional,integral, and differential) values from a stored pressure tablecorresponding to the target pressure, and adjust the throttle valveaccording to the PID values obtained from the pressure table.Alternatively, the pressure control subroutine 470 can be written toopen or close the throttle valve to a particular opening size toregulate the reactor 10 to the desired pressure.

The heater control subroutine 480 comprises program code for controllingthe temperature of the heat modules or radiated heat that is used toheat the susceptor 12. The heater control subroutine 480 is also invokedby the chamber manager subroutine 440 and receives a target, or setpoint, temperature parameter. The heater control subroutine 480 measuresthe temperature by measuring voltage output of a thermocouple located ina susceptor 12, compares the measured temperature to the set pointtemperature, and increases or decreases current applied to the heatmodule to obtain the set point temperature. The temperature is obtainedfrom the measured voltage by looking up the corresponding temperature ina stored conversion table, or by calculating the temperature using afourth order polynomial. The heater control subroutine 480 graduallycontrols a ramp up/down of current applied to the heat module. Thegradual ramp up/down increases the life and reliability of the heatmodule. Additionally, a built-in-fail-safe mode can be included todetect process safety compliance, and can shut down operation of theheat module if the reactor 10 is not properly set up.

The plasma control subroutine 490 comprises program code for setting theRF bias voltage power level applied to the process electrodes in thereactor 10, and optionally, to set the level of the magnetic fieldgenerated in the reactor. Similar to the previously described chambercomponent subroutines, the plasma control subroutine 490 is invoked bythe chamber manager subroutine 440.

The above CVD system description is mainly for illustrative purposes,and other plasma CVD equipment such as electrode cyclotron resonance(ECR) plasma CVD devices, induction-coupled RF high density plasma CVDdevices, or the like may be employed. Additionally, variations of theabove described system such as variations in susceptor design, heaterdesign, location of RF power connections and others are possible. Forexample, the wafer could be supported and heated by a resistively heatedsusceptor. The pretreatment and method for forming a pretreated layer ofthe present invention is not limited to any specific apparatus or to anyspecific plasma excitation method.

Deposition of the Oxidized Organosilane or Organosiloxane Dielectric ina Three-Layer Gap Filling Process

The oxidized organosilane or organosiloxane layer of the presentinvention can be used in a three-layer gap filling process as shown inFIG. 5 using the PECVD chamber of FIG. 2. Referring to FIG. 5, a waferis positioned 200 in the reactor 10 and an oxidized organosilane layerhaving a low dielectric constant is deposited 205 by a PECVD processfrom a plasma comprising an organosilane compound and/or aorganosiloxane compound. The deposition step 205 can include acapacitively coupled plasma or both an inductively and a capacitivelycoupled plasma in the process chamber 15 according to methods known inthe art. An inert gas such as helium is commonly used in the PECVDdeposition to assist in plasma generation. A gap fill layer is thendeposited 210 on the liner layer by known methods. The gap fill layer ispreferably self-planarizing, such as spin-on polymers or oxidesdeposited in liquid form by reaction of methyl silane and hydrogenperoxide. A cap layer is then deposited 215 on the gap fill layer,preferably using the same process for depositing the lining layer. Thewafer is then removed 220 from the reactor 10.

Referring to FIGS. 6A-6E, the three-layer gap filling process provides aPECVD lining layer 300 of the oxidized organosilane or organosiloxanepolymer. The lining layer 300 acts as an isolation layer between asubsequent gap fill layer 302 and the underlying substrate surface 304and metal lines 306, 308, 310 formed on the substrate surface. The gapfill layer 302 is capped by a PECVD capping layer 312 of the oxidizedorganosilane or organosiloxane polymer. This process is implemented andcontrolled using a computer program stored in the memory 38 of acomputer controller 34 for a CVD reactor 10.

Referring to FIG. 6A, the PECVD lining layer 300 is deposited in thereactor 10 by introducing an oxidizing gas such as N₂O, an organosilaneor organosiloxane compound such as CH₃SiH₃ or (CH₃)₂SiH₂, and a carriergas such as helium. The substrate is maintained at a temperature of fromabout −20° C. to about 400° C., and preferably is maintained at atemperature of approximately −20° C. to 40° C. throughout the depositionof the PECVD lining layer. The PECVD lining layer 300 is deposited witha process gas that includes a mixture of the organosilane and/ororganosiloxane compound at a flow rate of about 5 sccm to about 500 sccmand the oxidizing gas at a flow rate of about 5 sccm to about 2000 sccm.The process gases are carried by an inert gas such He, Ar, Ne, or arelatively inert gas such as nitrogen, which are typically notincorporated into the film, at a flow rate of from about 0.2 to about 20lpm. The process gases react at a pressure from about 0.2 to about 20Torr, preferably less than 10 Torr, to form a conformal silicon oxidelayer on the substrate surface 304 and metal lines 306, 308, 310. Thereaction is plasma enhanced with a power density ranging from 0.05 W/cm²to 1000 W/cm², preferably a power density less than about 1 W/cm², mostpreferably a power density ranging from about 0.1 to about 0.3 W/cm².

For an 8″ single wafer chamber, the high frequency RF source ofapproximately 13.56 MHz is preferably connected to a gas distributionsystem and driven at about 10 to about 500 W while a low frequency RFsource of about 350 KHz to 1 MHz is optionally connected to a susceptorand driven at about 0 to about 100 W. In a preferred embodiment, thehigh frequency RF source is driven at about 20 W to about 250 W ofpulsed RF power, and the low frequency RF source is driven at about 0 toabout 50 W of pulsed RF power at a duty cycle from 10% to 30%. Thepulsed RF power is preferably cycled in short intervals, most preferablyhaving a frequency less than about 200 Hz. When the high frequency RFpower is constant, the power level preferably ranges from about 20 W toabout 100 W.

The oxidized organosilane or organosiloxane layer is then cured at apressure less than about 10 Torr a temperature from about 100° C. toabout 450° C. Optionally, curing could be conducted after deposition ofadditional dielectric layers.

The above process conditions result in the deposition of a PECVD lininglayer 300 (at about 2000 Å per minute) with improved barriercharacteristics for the subsequent deposition of the gap filling layer302 shown in FIG. 6B. The lining layer obtained from methylsilane hassufficient C—H bonds to be hydrophobic, and is an excellent moisturebarrier. Deposition of a hydrophobic lining layer has a surprising andunexpected result of converting subsequent hydrophilic layers tohydrophobic layers.

The process gases for the gap filling layer 302 are preferably SiH₄,CH₃SiH₃, or (CH₃)₂SiH₂ and 50 wt % of hydrogen peroxide (H₂O₂) which isvaporized and mixed with an inert carrier gas, such as helium. However,the gap filling layer can be any dielectric layer which has anacceptable dielectric constant. Alternative silicon containing compoundscan be used if byproducts are vapors at deposition conditions. Preferredalternative compounds incorporate oxysilano or silano groups, such as:

-   -   trimethylsilane,    -   disilanomethane,    -   bis(methylsilano)methane,    -   1,2-disilanoethane,    -   2,2-disilanopropane,    -   1,3,5-trisilano-2,4,6-trimethylene (cyclic),    -   1,3-bis(silanomethylene)siloxane,    -   bis(1-methyldisiloxanyl)methane,    -   1,3,5,7-tetramethylcyclotetrasiloxane, or    -   1,2-disilanotetrafluoroethane.

The process gas flows range from 0-2000 sccm for He, 10-200 sccm forCH₃SiH₃, and 0.1 to 3 g/min. for H₂O₂. The preferred gas flows rangefrom 100-500 sccm for He, 20-100 sccm for CH₃SiH₃, and 0.1 to 1 g/min.for H₂O₂. These flow rates are given for a chamber having a volume ofapproximately 5.5 to 6.5 liters. Preferably, reactor 10 is maintained ata pressure of about 0.2 to about 5 torr during deposition of the gapfilling layer 302. The gap filling layer 302 may be partially cured asshown in FIG. 6C to remove solvents such as water prior to deposition ofa cap layer 312 as shown in FIG. 6D. Curing is done in the reactor 10 bypumping under an inert gas atmosphere under 10 Torr.

Gap filling layers produced from methylsilane are typically hydrophilicand have poor moisture barrier properties. When deposited on a lininglayer produced from methylsilane, a gap filling layer produced frommethylsilane surprisingly is hydrophobic and has good moisture barrierproperties.

Referring to FIG. 6D, after deposition of the gap filling layer 302, thereactor 10 optionally resumes deposition of the oxidized organosilane ororganosiloxane layer of the present invention for deposition of acapping layer 312. Referring to FIG. 6E, after deposition of the cappinglayer, if any, the deposited layers are cured in a furnace or anotherchamber at a temperature from about 100° C. to about 450° C. to driveoff remaining solvent or water. Of course, processing conditions willvary according to the desired characteristics of the deposited films.

Deposition of a Dual Damascene Structure

A dual damascene structure which includes an oxidized organosilane ororganosiloxane layers as an etch stop or as an intermetal dielectriclayer is shown in FIG. 7. When the oxidized organosilane ororganosiloxane is used as an etch stop, a first dielectric layer 510 isdeposited on a substrate 512 and then the oxidized organosilane ororganosiloxane etch stop 514 is deposited on the first dielectric layerand cured. The etch stop is then pattern etched to define the openingsof the contacts/vias 516. A second dielectric layer 518 is thendeposited over the patterned etch stop and then pattern etched byconventional methods to define the interconnect lines 520. A single etchprocess is then performed to define the interconnects down to the etchstop and to etch the unprotected dielectric exposed by the patternedetch stop to define the contacts/vias.

Referring again to FIG. 7, the damascene structure alternativelyincludes the oxidized organosilane or organsiloxane as an intermetaldielectric. A first dielectric layer 510, preferably consisting of theoxidized organosilane or organosiloxane, is deposited on a substrate 512and then a conventional silicon oxide, silicon nitride, or hydrogenatedsilicon carbide etch stop 514 is deposited on the first dielectriclayer. The etch stop is then patterned to define the openings of thecontacts/vias 516. A second dielectric layer 518, consisting of theoxidized organosilane or organosiloxane, is then deposited over thepatterned etch stop and then patterned to define the interconnect lines520. A single etch process is then performed to define the interconnectsdown to the etch stop and to etch the unprotected dielectric exposed bythe patterned etch stop to define the contacts/vias.

A preferred dual damascene structure fabricated in accordance with theinvention includes a lining layer as shown in FIG. 8H, and the method ofmaking the structure is sequentially depicted schematically in FIGS.8A-8H, which are cross sectional views of a substrate having the stepsof the invention formed thereon.

As shown in FIG. 8A, an initial first dielectric layer 510, such asparylene, FSG, silicon oxide, or the like, is deposited on the substrate512 to a thickness of about 5,000 to about 10,000 Å, depending on thesize of the structure to be fabricated. As shown in FIG. 8B, the low ketch stop 514, which is the oxidized organosilane or organosiloxanelayer, is then deposited on the first dielectric layer to a thickness ofabout 200 to about 1000 Å using low levels of RF power. The low k etchstop 514 is then pattern etched to define the contact/via openings 516and to expose first dielectric layer 510 in the areas where thecontacts/vias are to be formed as shown in FIG. 8C. Preferably, low ketch stop 514 is pattern etched using conventional photolithography andetch processes using fluorine, carbon, and oxygen ions. After low k etchstop 514 has been etched to pattern the contacts/vias and the photoresist has been removed, a second dielectric layer 518 is deposited overetch stop 514 to a thickness of about 5,000 to about 10,000 Å as shownin FIG. 8D. A second dielectric layer 518 is then patterned to defineinterconnect lines 520, preferably using conventional photolithographyprocesses with a photo resist layer 522 as shown in FIG. 8E. Theinterconnects and contacts/vias are then etched using reactive ionetching or other anisotropic etching techniques to define themetallization structure (i.e., the interconnect and contact/via) asshown in FIG. 8F. Any photo resist or other material used to pattern theetch stop 514 or the second dielectric layer 518 is removed using anoxygen strip or other suitable process.

The metallization structure is then formed with a conductive materialsuch as aluminum, copper, tungsten or combinations thereof. Presently,the trend is to use copper to form the smaller features due to the lowresistivity of copper (1.7 μΩ-cm compared to 3.1 μΩ-cm for aluminum).Preferably, as shown in FIG. 8G, a suitable barrier layer 524 such astantalum nitride is first deposited conformally in the metallizationpattern to prevent copper migration into the surrounding silicon and/ordielectric material. Thereafter, copper 526 is deposited using eitherchemical vapor deposition, physical vapor deposition, electroplating, orcombinations thereof to form the conductive structure. Once thestructure has been filled with copper or other metal, the surface isplanarized using chemical mechanical polishing, as shown in FIG. 8H.

Deposition of Adhesive Layers

A dual damascene structure which includes an oxidized organosilane ororganosiloxane layer as an adhesive layer between a premetal dielectriclayer and an intermetal dielectric layer is shown in FIG. 9. Theoxidized organosilane or organosiloxane adhesive layer 612 is depositedon a premetal dielectric layer 610 such as a conventional PSG or BPSGlayer and then cured. An intermetal dielectric layer 614, preferably alow k dielectric polymer layer, is then deposited over the adhesivelayer 612. A conventional silicon oxide or silicon nitride etch stop 616is then patterned by conventional methods to define vias 620. A secondintermetal dielectric layer 622, preferably the low k dielectricpolymer, is then deposited over the patterned etch stop and thenpatterned to define the interconnect lines. A single etch process isthen performed to define the interconnects down to the etch stop and toetch the unprotected dielectric exposed by the patterned etch stop todefine the contacts/vias prior to metallization.

A preferred dual damascene structure comprising an adhesive layer inaccordance with the invention is shown in FIG. 10H, and the method ofmaking the structure is sequentially depicted schematically in FIGS.10A-10H, which are cross sectional views of a substrate having the stepsof the invention formed thereon.

As shown in FIG. 10A, an initial first intermetal dielectric layer 710,such as parylene, FSG, silicon oxide, or the like, is deposited on asubstrate 712 to a thickness of about 5,000 to about 10,000 Å, dependingon the size of the structure to be fabricated. As shown in FIG. 10B, alow k adhesive layer 714, which is the oxidized organo silane layer, isthen deposited on the first intermetal dielectric layer 710 to athickness of about 50 to about 200 Å. A conventional silicon oxide orsilicon nitride etch stop 716 is the deposited on the adhesive layer 714to a thickness of about 50 to about 200 Å. A second low k adhesive layer718, which is the oxidized organo silane layer, is then deposited on theetch stop 716 to a thickness of about 50 to about 200 Å. The etch stop716 and adhesive layers 714, 718 are then pattern etched to define thecontact/via openings 720 and to expose first intermetal dielectric layer710 in the areas where the contacts/vias are to be formed as shown inFIG. 10C. Preferably, the etch stop 716 is pattern etched usingconventional photolithography and etch processes using fluorine, carbon,and oxygen ions. After the etch stop 716 and adhesive layers 714, 718have been etched to pattern the contacts/vias and the photo resist hasbeen removed, a second intermetal dielectric layer 722 is deposited oversecond adhesive layer 718 to a thickness of about 5,000 to about 10,000Å as shown in FIG. 10D. The second intermetal dielectric layer 722 isthen patterned to define interconnect lines 724, preferably usingconventional photolithography processes with a photo resist layer 726 asshown in FIG. 10E. The interconnects and contacts/vias are then etchedusing reactive ion etching or other anisotropic etching techniques todefine the metallization structure (i.e., the interconnect andcontact/via) as shown in FIG. 10F. Any photo resist or other materialused to pattern the etch stop 716 or the second intermetal dielectriclayer 722 is removed using an oxygen strip or other suitable process.

The metallization structure is then formed with a conductive materialsuch as aluminum, copper, tungsten or combinations thereof. Presently,the trend is to use copper to form the smaller features due to the lowresistivity of copper (1.7 μΩ-cm compared to 3.1 μΩ-cm for aluminum).Preferably, as shown in FIG. 10G, a suitable barrier layer 728 such astantalum nitride is first deposited conformally in the metallizationpattern to prevent copper migration into the surrounding silicon and/ordielectric material. Thereafter, copper is deposited using eitherchemical vapor deposition, physical vapor deposition, electroplating, orcombinations thereof to form the conductive structure. Once thestructure has been filled with copper or other metal, the surface isplanarized using chemical mechanical polishing, as shown in FIG. 10H.

Dual Damascene Integration

Another preferred dual damascene structure comprises silicon oxidelayers having different dielectric constants to resist crosstalk betweenlayers, and is deposited as shown in FIGS. 11A-11D, which are crosssectional views of a substrate having the steps of the invention formedthereon.

As shown in FIG. 11A, a via level dielectric layer 810, having a carboncontent greater than 20% by atomic weight, is deposited on a substrate812 to a thickness of about 5,000 to about 10,000 Å, depending on thesize of the structure to be fabricated. The via level dielectric layeris preferably deposited by reacting N₂O and trimethylsilane at an RFpower level of 500 W with a duty cycle of 10%. As shown in FIG. 11A, thevia level dielectric level is then pattern etched to form the vias andcontact holes 814 with conventional photolithography and etch processesfor high carbon materials using fluorine, carbon, and oxygen ions.

As shown in FIG. 11B, trench level dielectric layer 822 having a carboncontent less than 10% by atomic weight, is deposited over the via leveldielectric layer 810 to a thickness of about 5,000 to about 10,000 Å.The trench level dielectric layer is preferably deposited by reactingN₂O and methylsilane at an RF power level of 500 W with a duty cycle of30%. The trench level dielectric layer 822 is then pattern etched todefine interconnect lines 824 as shown in FIG. 11B, using conventionalphotolithography processes and etch processes that are effective for lowcarbon materials and not effective for high carbon materials. Any photoresist or other material used to pattern the dielectric layers isremoved using chemical mechanical polishing, an oxygen strip, or othersuitable process.

The metallization structure is then formed with a conductive materialsuch as aluminum, copper, tungsten or combinations thereof. Presently,the trend is to use copper to form the smaller features due to the lowresistivity of copper (1.7 μΩ-cm compared to 3.1 μΩ-cm for aluminum).Preferably, as shown in FIG. 11C, a suitable barrier layer 828 such astantalum nitride is first deposited conformally in the metallizationpattern to prevent copper migration into the surrounding silicon and/ordielectric material. Thereafter, copper 830 is deposited as shown inFIG. 11D using either chemical vapor deposition, physical vapordeposition, electroplating, or combinations thereof to form theconductive structure. Once the structure has been filled with copper orother metal, the surface is planarized using chemical mechanicalpolishing or other planarizing methods.

The invention is further described by the following examples.

EXAMPLE

The following example and demonstrates deposition of an oxidizedorganosilane or organosiloxane film having excellent barrier andadhesion properties. This example was undertaken using a chemical vapordeposition chamber, and in particular, a “CENTURA DxZ” system whichincludes a solid-state RF matching unit with a two-piece quartz processkit, both fabricated and sold by Applied Materials, Inc., Santa Clara,Calif.

Non-Pulsed RF Power

An oxidized dimethylsilane film was deposited at a chamber pressure of3.0 Torr and temperature of 15° C. from reactive gases which were flowedinto the reactor as follows:

Dimethylsilane, (CH₃)₂SiH₂, at  55 sccm Nitrous oxide, N₂O, at  300 sccmHelium, He, at 4000 sccm.The substrate was positioned 600 mil from the gas distributionshowerhead and 20 W of high frequency power (13 MHz) was applied to theshowerhead for plasma enhanced deposition of an oxidized dimethylsilanelayer. The oxidized dimethylsilane material had a dielectric constant ofabout 2.5 and was hydrophobic.

Hypothetical Examples

The following hypothetical examples describe deposition of an oxidizedorganosilane or organosiloxane film of the present invention. Theseexamples are written for the chemical vapor deposition chamber describedin the prior example.

Pulsed RF Power

An oxidized 1,3,5-trisilano-2,4,6-trimethylene (cyclic) film isdeposited at a chamber pressure of 3.0 Torr and temperature of 15° C.from reactive gases which flow into the reactor as follows:

1,3,5-trisilano-2,4,6-trimethylene,  20 sccm —(—SiH₂CH₂—)₃— (cyclic), atNitrous oxide, N₂O, at  300 sccm Helium, He, at 4000 sccm.The substrate is positioned 600 mil from the gas distribution showerheadand 50 W of pulsed high frequency power (13 MHz) is applied to theshowerhead for plasma enhanced deposition of an oxidized1,3,5-trisilano-2,4,6-trimethylene layerPulsed RF Power

An oxidized 1,3-dimethyldisiloxane film is deposited at a chamberpressure of 3.0 Torr and temperature of 15° C. from reactive gases whichare flowed into the reactor as follows:

1,3-Dimethyldisiloxane,  30 sccm CH₃—SiH₂—O—SiH₂—CH₃, at Nitrous oxide,N₂O, at  300 sccm Helium, He, at 4000 sccm.The substrate is positioned 600 mil from the gas distribution showerheadand 50 W of pulsed high frequency RF power (13 MHz) is applied to theshowerhead for plasma enhanced deposition of an oxidizeddimethyldisiloxane layer.Microwave/RF Power

An oxidized 1,3-dimethyldisiloxane film is deposited at a chamberpressure of 3.0 Torr and temperature of 15° C. from reactive gases whichare flowed into the reactor as follows:

1,3-Dimethyldisiloxane,  30 sccm CH₃—SiH₂—O—SiH₂—CH₃, at Nitrous oxide,N₂O, at  300 sccm Helium, He, at 4000 sccm.Prior to entering the chamber, the nitrous oxide is dissociated in amicrowave applicator that provides 2000 W of microwave energy. Thesubstrate is positioned 600 mil from the gas distribution showerhead and50 W of high frequency RF power (13 MHz) is applied to the showerhead incycles for plasma enhanced deposition of an oxidized dimethyldisiloxanelayer. Each cycle provides RF power for 30% of the cycle.

While the foregoing is directed to preferred embodiments of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims which follow.

1. A method for depositing an intermetal dielectric layer on asemiconductor substrate, the method comprising: reacting anorganosilicon compound and an oxidizing gas at RF plasma conditionssufficient to deposit an intermetal dielectric layer on thesemiconductor substrate, wherein the organosilicon compound comprisesone or more silicon atoms and two methyls bonded to each silicon atom,the RF plasma conditions comprise a power density less than 1 W/cm², andthe intermetal dielectric layer has a carbon content of from 1% to 50%by atomic weight and a dielectric constant of less than
 3. 2. The methodof claim 1, wherein the RF plasma conditions comprise a power densityranging from 0.1 W/cm²to 0.3 W/cm².
 3. The method of claim 1, whereinthe RF plasma conditions comprise a substrate temperature of from −20°C. to 400° C.
 4. The method of claim 1, wherein the organosiliconcompound is dimethylsilane.
 5. The method of claim 1, wherein the RFplasma conditions comprise mixed frequency RF power.
 6. The method ofclaim 1, wherein the organosilicon compound is dimethylsilanediol. 7.The method of claim 1, wherein the oxidizing gas is selected from thegroup consisting of oxygen and nitrous oxide.
 8. The method of claim 1,wherein the oxidizing gas is oxygen.
 9. A method for depositing adielectric layer on a semiconductor substrate, the method comprising:reacting an organosilicon compound and an oxidizing gas at RF plasmaconditions sufficient to deposit a dielectric layer on the semiconductorsubstrate, wherein the organosilicon compound comprises one or moresilicon atoms and two methyls bonded to each silicon atom, the RF plasmaconditions comprise a power density less than 1 W/cm², and thedielectric layer has a carbon content of from 1% to 50% by atomic weightand a dielectric constant of less than 3; etching the dielectric layerto define an interconnect; and filling the interconnect with aconductive material.
 10. The method of claim 9, wherein the RF plasmaconditions comprise a power density ranging from 0.1 W/cm² to 0.3 W/cm².11. The method of claim 9, wherein the RF plasma conditions comprise asubstrate temperature of from −20° C. to 400° C.
 12. The method of claim9, wherein the organosilicon compound is dimethylsilane.
 13. The methodof claim 9, wherein the RF plasma conditions comprise mixed frequency RFpower.
 14. The method of claim 9, wherein the organosilicon compound isdimethylsilanediol.
 15. The method of claim 9, wherein the oxidizing gasis selected from the group consisting of oxygen and nitrous oxide. 16.The method of claim 9, wherein the oxidizing gas is oxygen.